In optical lithography, small space patterning is the most difficult task. The direct small-space patterning is not good enough with resolution enhancement technique (RET) in sub-80 nm level. Two sequential processes normally achieve the small space. Once the pattern is forming a larger pattern normally, and then makes them shrink to fit to the designed size by additional process. Usually resist thermal flow process has been used to obtain small space as additional process, which has several process issues such as flow amount control of isolated and dense small contacts, uniformity degradation and bowing profile. In order to solve these issues, we introduced the resolution enhancement lithography assisted by chemical shrink (RELACS) and shrink assist film for enhancement resolution (SAFIER) process in ArF lithography. In this paper, the RELACS and SAFIER process are compared with the resist thermal flow process for sub-80 nm space using ArF exposure tool. With the application of this process, we confirmed the improvement of in-wafer uniformity and the successful implementation of sub-80nm small space patterning regardless of pitch size and pattern arrangement.
The introduction of ArF lithography in device manufacturing has been studied with a low k1-factor. There are a number of issues that must be resolved to ensure the successful implementation of this technology. Such issues include the reduction in resist thickness and organic bottom anti-reflective coating (BARC) due to the characteristics of ArF resist with lower etch resistance in comparison with that of KrF. Requirements of a suitable high-performance of thin organic BARC material include chemical reactions with sub-layer, simulation for the minimization of reflectance, faster etch rate, and compatibility with resist. The optimum refractive index (n) and the extinction coefficient (k) of thin organic BARC are simulated to match the optical properties of substrates. These values are satisfied with the reflectance less than 2% at 1st minimum. In the case of SiN sub-layer with acid absorption capability, it is confirmed that the chemical reaction with thin organic BARC has an effect on line edge roughness (LER) and pattern profile. Also, the degree of these effects is dependent upon the acidity of thin organic BARC. In this paper, it is shown that the application of thin organic BARC to sub-90nm patterning in ArF lithography is very feasible and adaptable in the view of lithographic and etch performance.